The broad objectives of the proposed randomized clinical trial are to appropriately reduce hospitalization of low-risk patients and to improve the quality of care for patients with CAP treated in hospital emergency departments (EDs). This trial compares two quality improvement interventions that use the same project-designed guideline and are implemented in conjunction with the two participating state PROs. Hospital EDs will be randomized to receive one of two active quality improvement interventions. An experimental guideline implementation strategy, or (2) a hospital-designed strategy, which relies on standard PRO methods for quality improvement. The specific aims of the clinical trial are (1) to compare the effectiveness of the experimental guideline implementation strategy and the hospital-designed strategy in decreasing the proportion of low-risk patients treated in the hospital; (2) to compare the medical outcomes, cost of care, and cost of study interventions for patients treated in EDs randomized to receive of the two interventions, and (3) to compare the effectiveness of the two interventions in increasing medical providers' adherence to processes of care recommended by the project guideline. The primary hypotheses guiding this study are that the experimental guideline implementation strategy, in comparison with the hospital- designed strategy, will decrease the proportion of low-risk patients with CAP who are treated as in-patients, and increase the performance of processes of care recommended by the project guideline. The secondary hypotheses are that patients treated at EDs using the experimental guideline implementation strategy, in comparison to those treated at sites using the hospital-designed strategy, will have equivalent to superior medical outcomes and total cost of care. This trial is likely to lead to an appropriate reduction in hospital admission rates and improvements in the processes of care for patients with CAP. If the experimental guideline implementation strategy improves quality more cost-effectively than the hospital-designed strategy, than PROs, hospitals, and/or managed care organizations throughout the United States would be likely to replicate this experimental strategy. Given increasing pressures to improve medical quality and decrease cost, the study findings could have broad applications to other illnesses that demonstrate excessive rates of hospitalization and/or under-performance of important processes of care.